code: def test_mesh_normals_empty():
      mesh = scene.visuals.Mesh()
      scene.visuals.MeshNormals(mesh.mesh_data)
  
file_path: vispy/vispy/visuals/tests/test_mesh_normals.py
imports: import numpy
  import pytest
  from vispy import scene
  from vispy.geometry import create_sphere
  from vispy.testing import TestingCanvas, requires_application, run_tests_if_main, requires_pyopengl
label_desc: Use image node_id 6 for calling a global function with example usage: test_mesh_normals_empty() without return types